Inner–outer directions are labels that identify the direction of travel on opposing lanes of traffic on certain ring roads or beltways. They can be used to sign individual routes that encircle a city or metropolitan area, where east–west and north–south orientations cannot be applied uniformly. The labels are also used in select double track rail systems that form a loop, indicating the direction of travel of each line. Variations of the labels include "inner loop" or "outer loop", "inner beltline" or "outer beltline", "inner ring" or "outer ring", "inner rail" or "outer rail", and "inner circle" or "outer circle". In 2009, Interstate 277 in Charlotte, North Carolina, became the first non-contiguous loop route to utilize inner–outer directional signage.
Concept
In nations where automobiles drive on the right side of a road, traffic traveling in a clockwise direction around a loop will always be in the "inner" lane. Likewise, traffic traveling in a counterclockwise direction will always be in the "outer" lane. "Inner" and "outer" labels stem from this reasoning, applying the concept of concentric loops to the geographic characteristics of circular road or rail.
Criticism and alternatives
Despite the logical benefits and uniformity of inner/outer labeling, many find the concept confusing, especially those in nations where compass directions are by far more commonly used to sign routes. More confusion can occur in places where more than one route encircles an area ; the outermost route may be called an Outer Loop and the innermost route may be called an Inner Loop, causing confusion with the labels. The labeling system is also rarely used, so travelers are largely unfamiliar with the terms. As a result, most applications of inner and outer are secondary to compass directions, which change as one travels along the loop. Most beltways in the United States do not use inner–outer directions, since compass directions are the predominant way to designate direction on numbered routes. Beltways with a single number for the entire route, such as Interstate 285 in the Atlanta area, are generally given compass directions that change as one travels along the route. A special case is the beltway for Twin Cities which was numbered before it was common to use a single number for an entire beltway. That road is split into northern and southern halves for numbering purposes, with Interstate 694 assigned to the northern and eastern half and Interstate 494 assigned to the southern and western half. Both halves are posted with east and west directions on their entire lengths. However, the milemarkers for those Interstates treat them as a single highway, beginning at the Minnesota River bridge on I-494, increasing going clockwise and including I-694, returning to the Minnesota River bridge on I-494. The Meijō Line inNagoya, Japan uses the terms clockwise and counterclockwise. Hong Kong's Transport Department employs yet another method of orbital road signing: clockwise traffic on Route 9 is denoted by the letter "A", while counterclockwise traffic is denoted by the letter "B".
Examples
Inner and outer directions may be used as the primary labeling system for routes or as a system secondary to another system such as compass directions.
